Follow-up Tc-99 m pyrophosphate cardiac scan for patients with transthyretin cardiac amyloidosis treated with tafamidis

BackgroundTafamidis has been used for treatment of transthyretin cardiac amyloidosis (ATTR-CA). However, Tc-99 m pyrophosphate (PYP) cardiac scan for follow-up after tafamidis therapy has not been reported.MethodsFrom May 2017 to March 2022, five patients with or without tafamidis therapy had received two Tc-99 m PYP cardiac scans. Tc-99 m PYP cardiac scan was performed with planar image and single photon emission computed tomography/computed tomography (SPECT/CT) 3 h after administration of Tc-99 m PYP. Perugini grading system was applied to determine positive or negative result of the scan. Heart to contralateral lung (H/CL) ratio as well as the difference of H/CL ratio between first and second Tc-99 m PYP cardiac scans (Delta H/CL ratio) was calculated.ResultsIn the five patients participated in this study, three received tafamidis therapy and H/CL ratio was significantly decreased (p = 0.02) after tafamidis therapy. Besides, the Delta H/CL ratio was larger in patients with tafamidis therapy than that in those without tafamidis therapy, albeit not reaching statistical significance (p = 0.2).ConclusionA decrease in H/CL ratio was found after tafamidis therapy in patients with ATTR-CA, albeit the magnitude of changes in the H/CL ratio (Delta H/CL ratio) was not significantly different from that of patients without tafamidis therapy. Future study with larger population might be required to further clarify the effect of tafamidis therapy on myocardial uptake of Tc-99 m PYP.